[quote="AshyRaccoon":2dr2t0ys]I wonder if the space savings would be that different between a zip (or rar, 7z, etc.), containing a cap which has all the graphics embedded in it, versus a zip containing a cap and all the maximum-compressed png files?[/quote:2dr2t0ys]
png and jpg are specialized image compression techniques, so normally they will be smaller than their zip and rar counterparts. Also, rar can compress with a 'multimedia' algorithm but only can use one (among several other types) such algorithm per file, which means the rest of the cap won't compress well, further increasing the resulting size.
You're better off using specialized compression, unless you really don't want to expose the file (but you could stash pngs and jpgs in a zip file and rename it to something.dat)